1. Field of the Invention
The present invention relates to an electronic endoscope system including an elongate flexible scope having a solid-state image sensor provided at a distal end thereof to generate image-pixel signals, and an image-signal processing unit that produces a video signal on the basis of the image-pixel signals.
2. Description of the Related Art
In such an electronic endoscope system, a CCD (charge-coupled-device) image sensor is usually utilized as the solid-state image sensor, and is associated with an objective lens system provided at the distal end of the flexible scope. Also, a flexible optical guide, formed of a bundle of optical fibers, is extended through the flexible scope, and is associated with a lighting lens system provided at the distal end of the flexible scope.
The image-signal processing unit includes a light source, such as a halogen lamp, a xenon lamp or the like, and when the flexible scope is connected to the image-signal processing unit, the proximal end of the optical light guide is optically connected to the light source. Thus, an object to be sensed by the CCD image sensor is illuminated by light radiating from the distal end of the optical light guide, and is focused as an optical image on a light-receiving surface of the CCD image sensor, by the objective lens system.
The focused optical image is converted into a frame of analog image-pixel signals by the CCD image sensor, and the frame of analog image-pixel signals is read from the CCD image sensor at successively given regular time intervals. The successively-read frames of image-pixel signals are then fed to the image-signal processing unit, in which the frames of image-pixel signals are suitably processed to produce a video signal. The video signal is then fed from the image-signal processing unit to a TV monitor, to reproduce an endoscope-image on the screen of the TV monitor.
Recently, in the electronic endoscope system, a specific wavelength light source may be substituted for the white light source to perform a specific medical examination. For example, an ultraviolet lamp is used as the specific wavelength light source to find cancer tissue from among internal tissue of a person. In particular, when internal tissue of a person is irradiated with UV light, the irradiated tissue generates fluorescence. The intensity of the fluorescence, derived from healthy tissue, is greater than that of the fluorescence derived from cancerous tissue. Thus, cancerous tissue cain be found by illuminating internal tissue with the ultraviolet light and by reproducing the fluorescent images on the screen of the TV monitor.
In this case, it is frequently necessary to compare an image, based on the white light illumination, with a fluorescent image based on the ultraviolet light illumination, before a cancer tissue can be accurately and precisely found. Thus, this medical examination necessitates two electronic endoscope systems using a white light source and an ultraviolet source, and thus is very costly.
Furthermore, it is desirable to repeatedly perform a comparison between the normal image and the fluorescent image at frequent intervals, but this method of medical examination is practically impossible because the two scopes usually cannot be inserted in the patient body at the same time.
Therefore, an object of the present invention is to provide a novel electronic endoscope system utilizing both a usual white light source and a specific wavelength light source, which is constituted such that the usual white light source and the specific wavelength light source are quickly switched between each other.
In accordance with an aspect of the present invention, there is provided an electronic endoscope system, which comprises: a scope having an image sensor provided at a distal end thereof to generate image-pixel signals; an image-signal processing unit, to which a proximal end of the scope is connected, that processes the image-pixel signals to thereby produce a video signal; a light source device provided in the image-signal processing unit; and an optical light guide that extends through the scope, the optical light guide being optically connected to the light source device when the connection is established between the scope and the image-signal processing unit. The light source device includes a first light source that emits white light, a second light source that emits a specific wavelength light, and a light source switcher that selectively introduces either the white light or the specific wavelength light into the optical light guide.
Preferably, the light source switcher may include a light deflector, and a deflector-driving-mechanism that moves the light deflector between a first operative position and a second operative position. In this case, when the light deflector is positioned at the first operative position, the white light is introduced into the optical light guide. Also, when positioning the light deflector at the second operative position, the white light is blocked off by the light deflector, and the specific wavelength light is introduced by the light deflector into the optical light guide.
The light source switcher may further include an illumination mode selection system that selects one of a first illumination mode, in which the white light is introduced into the optical light guide, and a second illumination mode, in which the specific wavelength light is introduced into the optical light guide, and a controller that controls the deflector-driving-mechanism such that the light deflector is positioned at the first operative position when the first illumination mode is selected by the illumination mode selection system, and such that the light deflector is positioned at the second operative position when the second illumination mode is selected by the illumination mode selection system.
The light source device may further include a rotary color-filter/shutter, and a filter/shutter-driving-mechanism that moves the color-filter/shutter between a first operative position at which the color-filter/shutter functions as a rotary color filter and a second operative position at which the color-filter/shutter functions as a rotary shutter. The white light is converted into three primary color lights through the color-filter/shutter, positioned at the first operative position, whereby the three primary color lights are cyclically and sequentially introduced into the optical light guide. The specific wavelength light is cyclically and sequentially introduced into the optical light guide through the color-filter/shutter positioned at the second operative position.
The light source device may further include an illumination mode selection system that selects one of a first illumination mode, in which the white light is introduced into the optical light guide, and a second illumination mode, in which the specific wavelength light is introduced into the optical light guide, and a controller that controls the filter/shutter-driving-mechanism such that the color-filter/shutter is positioned at the first operative position when the first illumination mode is selected by the illumination mode selection system, and such that the color-filter/shutter is positioned at the second operative position when the second illumination mode is selected by the illumination mode selection system.
The rotary color-filter/shutter may comprise a disk element having-three primary color filters circumferentially spaced from each other at regular angular intervals. An area between two adjacent color filters is formed as a light-shielding area, and the light-shielding areas are radially and outwardly extended such that the extended areas form the rotary shutter. Optionally, only one of the light-shielding areas may be radially and outwardly extended such that the extended area forms the rotary shutter.
According to another aspect of the present invention, the light source device comprises a first light source that emits white light, a second light source that emits a-specific wavelength light, a light source switcher that selectively introduces one of the white light and the specific wavelength light into the optical light guide, and a rotary shutter associated with the second light source such that the rotary shutter is interposed in a specific wavelength-light path through which the specific wavelength light passes. The rotary shutter includes at least two light-shielding elements circumferentially spaced from each other at regular angular intervals and having different radial lengths. The light source device further comprises a shutter-driving-mechanism that relatively moves and positions the rotary shutter with respect to the specific-wavelength-light path such that the specific-wavelength-light path is selectively blocked off by the light-shielding elements having the different radial lengths, whereby an exposure time, during which the image sensor is illuminated with the specific wavelength blight, is varied.
Preferably, the light source device further comprises a rotary color filter interposed in a white-light path through which the white light passes, and a rotational frequency of the color filter is an integral multiple of that of the rotary shutter.
Preferably, the rotary shutter is moved by the shutter-driving mechanism between first and second relative positions with respect to the specific-wavelength-light path. When the rotary shutter is positioned at the first relative position, the specific-wavelength-light path is blocked off by a longer one of the light-shielding elements. When the rotary shutter is positioned at the second relative position, the specific-wavelength-light path is blocked off by both the light-shielding elements.
Preferably, the light source device further includes an exposure mode selection system that selects one of a first exposure mode, in which the specific-wavelength-light path is blocked off by the longer one of the light-shielding elements, and a second exposure mode, in which the specific-wavelength-light path being blocked off by both the light-shielding elements, and a controller that controls the shutter-driving-mechanism such that the rotary shutter is positioned at the first operative position when the first exposure mode is selected by the exposure mode selection system, and such that the rotary shutter is positioned at the second operative position when the second exposure mode is selected by the exposure mode selection system.